The role of NASA in commercial crew safety

By Jeff Foust on 2012 February 22 at 7:36 am ET

How active NASA should be in ensuring, or even regulating, the safety of commercial crew vehicles is an issue that has been debated for some time, but a couple of events in the last week demonstrate that the issue is still on the minds of people on Capitol Hill.

At last Friday’s hearing about the administration’s FY13 budget proposal for R&D programs, the first question posed to Office of Science and Technology Policy director John Holdren was not about proposed spending for NASA or other agencies, but about whether NASA had sufficient authority to oversee crew safety given its use of Space Act Agreements (SAAs). “I have a problem with this,” said committee chairman Rep. Ralph Hall (R-TX). “It’s my understanding that NASA can’t require the companies to meet any safety standards. I don’t know how that could have been left out.” Hall then asked Holden how NASA would ensure that these vehicles “ultimate are going to be safe enough to take NASA astronauts to the International Space Station?”

Holdren said he was not familiar with the details of the the limits of Space Act Agreements on enforcing compliance to safety standards. “I can’t imagine that NASA does not retain that responsibility” for ensuring crew safety, he said. “And if there is a problem in the agreements that would jeopardize that, I am sure we will fix it.”

At a Commercial Crew program forum at the Kennedy Space Center earlier this month, NASA officials said they were confident that safety would be ensured without mandating compliance, since it will be in the companies’ best interests to meet NASA’s published safety standards in order to qualify for future contracts for crew transportation that will require meeting those standards. “So, our safety requirements are on the street and we would expect that any partner that might want to go after that service capability, and any commercial partner that might want to use NASA and its ISS as a potential customer, will need to look seriously at those requirements and understand what they are and understand the safety parameters we have within those requirements,” deputy program manager Brent Jett said at the February 7 briefing.

A separate issue is the role of NASA versus the FAA in regulating commercial crew launches. Such a mission would likely be considered a commercial launch and thus require a license from the FAA’s Office of Commercial Space Transportation (AST), but one senator warned the FAA last week not to get more involved. “The FAA is going to be doing some of the regulations on this, but don’t think they’re going to be to the exclusion of NASA,” Sen. Bill Nelson (D-FL) said in a speech at the FAA’s 15th Annual Commercial Space Transportation Conference on Thursday. “When you start man-rating a rocket, NASA’s going to be all over them with all four feet,” a figure of speech that engendered a few chuckles from the audience.

“Now I will admit that I have been a skeptic about getting the FAA involved,” Nelson said later in his speech. “But if the FAA’s expertise can really help do the routine things, and stay out of the knickers of NASA, and let NASA provide the technical know-how to keep the missions and the payloads and the astronauts safe aboard these new launch vehicles, and let the FAA prepare the safety guidelines for the industry, then we ought to be alright. But if you get the FAA starting to want to do what NASA does, then we’ve got a problem.”

55 comments to The role of NASA in commercial crew safety

I think the Congessman’s aid hasn’t looked at the SSA’s objectives and requirements.

NASA is unable to levy exact requirements, it can however provide what standards it is looking for. If by some miracle all four spacecraft were available at the same time and two of them followed NASA suggested safety guidelines and two didn’t, I am betting NASA would down select to the two vehicles that followed the guidelines.

It is in the best interest of all of these companies to build vehicles that meet or exceed NASA’s standards. NASA is not obligated to fly any Astronauts on vehicles it deems unsafe.

Nelson’s comments about NASA getting involved in a regulatory role scares me. Unless it’s NASA people flying on-board, or a NASA destination (ISS) being visited, I think it’s wise to keep things the way they are, with NASA having no regulatory role whatsoever. The FAA at least has an active mandate to both promote safety and promote the industry. Giving NASA a bigger role in non-NASA commercial crew would be a great way to throttle that industry in its crib (in spite of NASA’s good intentions).

I think what Congress also forgets is that the goals of CCDev 1 & 2 are to buy down risk. They do that by paying CCDev participants to work on technology that NASA has deemed applicable to future Commercial Crew vehicles. Environmental systems, pusher-LAS systems, composite structures, etc.

The final filter for NASA to use is the CCiCap contract, where the applicants will have to show how they plan to build and operate their vehicles. As you pointed out, if NASA doesn’t like a contractors approach, they don’t have to choose them. With four participants, that provides a good amount of competition to meet NASA’s requirements.

So far I think the whole COTS/CCDev/CCiCap process is working pretty well, and is a fantastic value for the U.S. Taxpayer.

Hall must be headed into dementia. I am trying to figure out why after losing two shuttle orbiters, killing 14 crew members and having a plethora of near misses NASA “safety” is considered useful input anywhere.

In FEDERAL government safety courses NASA is routinely classed with the Russian Submarine force in terms of safety competence. The safety organization is dysfunctional and would last about two minutes at even a commercial airline…

I am trying to figure out why after losing two shuttle orbiters, killing 14 crew members and having a plethora of near misses NASA “safety” is considered useful input anywhere.

Seems to me the safety record is okay given that there were 135 flight on a vehicle with no practical abort modes. When you are juggling hand grenades you can’t expect perfection. I question whether one of the nickle and dime CCDev2 entrants can match it. It will be fun to watch.

Seems to me the safety record is okay given that there were 135 flight on a vehicle with no practical abort modes<

"We are running through all the pertubations of OPE but since there are multiple thousands of them we will be ploughing through them for several weeks Mr. President".

"How long until the bombers reach Soviet Airspace General"

"Less then 1 hour Mr. President"

(some interplay between General Turgidson and President Muffly Dr. Strangelove)

Either you know nothing or are just a NASA toady.

The two orbiters that were lost and the several near misses were not due to juggling hand grenades. That is perfectly safe. Dont pull the pin and you are fine…you can even throw them up against the wall.

COlumbia and Challenger and a few near misses were akin to pulling the pin releasing the handle and saying "wow wonder whats next".

The fact that they allowed a vehicle that has no practical abort modes to keep flying is the reason to worry, esp with such a fragile heatshield.

There is never going to be perfection or total safety, but its practical to get a vehicle that is more than 10 times safer than the Shuttle was. It will be even safer and cheaper.

The CCDEV entrants with much less money are designing far safer vehicles than the Shuttle without unstoppable RSRM’s and with escape systems that work all the way to orbit without another separation event to complicate matters.

“I question whether one of the nickle and dime CCDev2 entrants can match it.”

They’ll all be about an order of magnitude better just by dint of the fact that they were smart enough to incorporate abort systems. Maybe more depending on the track record of Atlas V and Falcon 9 prior to taking on crewed systems.

Robert G. Oler wrote @ February 22nd, 2012 at 11:49 am
“Hall must be headed into dementia. I am trying to figure out why after losing two shuttle orbiters, killing 14 crew members and having a plethora of near misses NASA “safety” is considered useful input anywhere.”

Because it was bad managment that lost both Challenger and Columbia– not poor safety issues. As you well know, in both instances, red flags flew, but managment chose to ignore them– in Challenger’s era, repeatedly tagging items as ‘acceptable flight risks’ in the face of repeated warning from engineers as a matter of keeping to schedule pressures to make it pay its way and in Columbia’s case- muddled decision-making coupled with costs associated with accessing outside assets. Commercials hasn’t killed anyone in spaceflight because they haven’t flown anybody. Given the profit motive behind all commerical firms, and the accompanying business plans dictating operating ‘close to the margin’ — when they start flying, they’ll start losing hardware, passengers and crews, too. It’s inevitable.

The CCDEV entrants with much less money are designing far safer vehicles than the Shuttle without unstoppable RSRM’s

There was 1 SRB failure out of 250 firings, and none in 25 years of operation. Get off of it. There is nothing safe about shutting down motors in hypersonic flight.

and with escape systems that work all the way to orbit without another separation event to complicate matters.

Pusher escape systems waste weight, and the negative stability requires sophisticated control. There are good reasons why NASA chose a puller system for Apollo and Ares. SpaceX demonstrated a pusher engine on a test stand last month. NASA successfully tested a fully integrated Orion escape system 2 years ago. What can you do. They have political cover, for now.

CSCA wrote @ February 22nd, 2012 at 2:21 pm
Given the profit motive behind all commerical firms, and the accompanying business plans dictating operating ‘close to the margin’ — when they start flying, they’ll start losing hardware, passengers and crews, too. It’s inevitable.”

HMM people think that…but I am not so sure it is an accurate reflection of events.

First off there really is nothing “Magic” about building a space operations vehicle…ie an “airplane” that works in space. The “rocket” is the semi hard part of the equation.

But I DONT see commercial; particularly a commercial operator that has a lot of money riding on a booster that also flies in essentially the same version taking many “short cuts” which would negate the reliability of the booster and hence the “money machine” that the booster has.

It doesnt make all that much solid economic sense. AS for the “flight operations” (ie the in space part of it) same thing. If an “event” occurs and in retrospect it is clearly seen as “risk taking” then the company is finished…and like an airline in an attempt to save themselves at least the people who made the bad decisions “go out the door”.

I dont disagree with what you wrote on the shuttle accidents; but I go a few steps farther.

What killed a couple of crews AND a few near misses that were plugged over…is an incompetence inside the agency in almost all respects; some third rate people running the thing,…..but most important a sort of “we are super people and we deserve a pass on things because we do super things”.

They speak that babble at NASA so much that they start to believe it…and finally it colors their decision making. They really do not deal in engineering reality any more. its “we do space and no one else can tell us what or how to do it because well we do space and space is hard”.

It is not that hard…it wasnt in Glenn’s era nor is it really today.

That attitude coupled with functional incompetents gets people killed.

IIRC, the Orion tractor-style LAS weighed around 20,000 lbs, which decreased the effective payload capacity of the Ares I so much they had to add SRM segments.

The Orion LAS was also single mode, in that it was needed for pulling the Orion off the rapidly accelerating (and unstoppable) Ares I rocket, but only during a limited part of the flight profile, not all of it like pusher LAS systems.

Pusher LAS systems are multi-mode, in that they act as an LAS throughout the entire flight profile to orbit, provide maneuvering in orbit, and in the case of the Dragon, could provide landing propulsion.

Back to the original discussion of roles and responsibilities, there is an ocean of difference between a R&D agency (NASA) and a regulatory agency (FAA). Sen. Nelson was wrong to discourage the FAA from doing their legislatively mandated job, and to do so at their own conference was an insult. If he wants to inhibit their scope of action, he should introduce legislation to prohibit them from prosecuting their mandate, not scolding them to stay out of NASA’s knickers. There is nothing particularly new or mysterious about space or safety. The FAA should take the lead, and NASA should be their enthusiastic partner.

One SRB failure too many. That hand-waving doesn’t comfort the families of the astronauts. A better designed system would have been both cheaper and safer, so thanks be to god that is what’s being invested in right now. SLS/Orion and CCDEV will both be safer systems than the Shuttle.

As regards to the weight, its not wasted as these systems can be used for orbital maneuvering and propulsive landing. The tower designs are wasteful as they are limited to when they can abort and cannot be reused later. They are less versatile and heavier than pusher system.

The Orion escape system alone weighs 6 tons, more than the entire Dragon capsule!!! Industry knows better than NASA in this regard and all the companies proposing commercial crew vehicles are going with Pusher systems.

Attention Master Musk! WaPo and HuffPo reports today portions of KSC is available for rent- the shuttle crawlers, launch pads and a shuttle runway! Throw a party or throw soem payloads up, out and away, Elon! Golly gee, all the stuff you need to start your own space program, there for the renting. Cabana says they’re too expensive to maintain and too costly to tear down.

“LOL Hard enough for comemrcial to have failed to yet launch, orbit and return a crew, half a century after Glenn flew.”

Not being a business-type of troll, you ignore the obvious reason – there hasn’t been a market for commercial crew, which is why no serious attempts were made to do any of the things you’re moaning about.

Even when there was a destination (the ISS), how could a commercial company compete with free? That’s the price NASA charged passengers for rides on the Shuttle. You can’t compete with the government, because the government has no need to recoup taxpayer money.

The commercial aerospace industry has built all of NASA’s space hardware, so it’s not a challenge for them to build and operate their own space hardware. Technology isn’t the barrier here, it’s more a matter of market issues and regulation, and those are being worked out through the COTS, CCDev and CCiCap initiative.

“Not being a business-type of troll, you ignore the obvious reason – there hasn’t been a market for commercial crew, which is why no serious attempts were made to do any of the things you’re moaning about.”

Not only that, the troll still has never shown me the documentation that someone like the astronaut farmer, could just build a freakin’ rocket and launch a human on it.

He STILL has never shown me the documentation from the FAA for a lic. regime that would allow someone to launch a human. I have only been asking him these same questions for 3 years… still no answer. tick tock

Where is the documentation from the military that they were fine with private citizens launching a human on a rocket? still nothing from the troll on that one.

Where is the documentation from NASA on the human ratings.. hell how many times did congress order them to create this? How many YEARS did it take for NASA to finally put something together on human ratings which is still not complete?

Where is the documentation from any government agency from the 1960’s, 1970’s, 1980’s that said the government not only would allow it.. but they would create the laws to allow it to happen..

ya want some tick tocks… well .. three years and still waiting .. tick tock

show me federal documents starting in the 1960’s that the federal government would allow citizens to build a freakin rocket in their backyard and launch a human on it… tick tock tick tock

In the last three years, SpaceX has provided and done more to answering his question than he has come to providing one single federal document that says private citizens were allowed to launch rockets with humans on them, starting in the 1960’s.

Why would SpaceX want to rent shuttle crawlers when they are using there own vertical lift launch crane for the Falcon 9?

It’s been fairly openly acknowledged now what I was told privately a few months ago, namely that SpaceX is talking with NASA about taking over LC-39A to launch the Falcon Heavy. Presumably they would use a VAB high bay to stack the Falcon Heavy and use a crawler to move it out to 39A.

SpaceX would need a platform to go on top of the crawler to move it to 39A. Three are available; I’m sure a deal would be made to modify a platform, or they’d build a new one.

One of the two crawlers is currently being modified to handle SLS; it’s in High Bay 2. The other sits outside.

1) keep firing and potentially collide with the MPCV through its abort apogee, or

2) be detonated, spewing burning fuel and creating a thermal environment that the MPCV’s parachutes are unlikely to survive.

Hmm, interesting. That is not stopping Boeing from flying the CST-100 on an Atlas V 412, which sports a large, dangerous, unstoppable SRB. My guess is they will add at least one more as the spacecraft inevitably gains weight.

Bob Steinke wrote @ February 22nd, 2012 at 6:27 pm
“What you should realize is that having a management culture that sweeps red flags under the rug IS a safety issue. It may be the most important safety issue.”

“It’s been fairly openly acknowledged now what I was told privately a few months ago, namely that SpaceX is talking with NASA about taking over LC-39A to launch the Falcon Heavy.”

Not surprising that they would want a separate launch pad from their current SLC-40 set up, which is specific to a single core rocket.

“Presumably they would use a VAB high bay to stack the Falcon Heavy and use a crawler to move it out to 39A.”

I think this question will be answered when they finish their Vandenberg AFB SLC-4E facility, as I think they will use the same setup on both coasts.

My guess is that they will stick with horizontal integration, although they may add some sort of tower that can be used to access payloads when the Falcon Heavy is raised into the vertical position prior to launch. Cost-wise, railroad truck sets and hydraulic lifters are a lot cheaper to operate than the VAB and crawler.

As a point of reference, Delta IV and Delta IV Heavy are integrated horizontally, then lifted at the pad, as are Proton and Soyuz. Atlas V is vertically integrated.

The most comprehensive standards ever established by NASA to ensure the safety and productivity of the crew were the Human-Systems Integration Standards, NASA Standard 3000. A long time ago the prescient JSC management, actually one manager in particular, decided to abolish the organization that had that responsibility for defining these crew safety requirements.

Recently JSC management is trying to re-establish a human-systems integration group. But there is no funding to pay for the function and the people, so they have formed an informal ‘employee support group’. The group can only meet on their lunch hour since management does not want to pay for this function. There are several employee support groups: for the gays, the hispanics, pacific islanders, and other minorities, and there is one for the group of people who are responsible for ensuring the safety and productivity of the crew. If it were not embarrassing and tragic it would be humorous.

So who is it that NASA is going to get to establish and ensure the standards for commercial crew?

“That is not stopping Boeing from flying the CST-100 on an Atlas V 412, which sports a large, dangerous, unstoppable SRB.”

It is a mark against the CST-100. But one, 1.5m Atlas V SRB producing under 1,300kN thrust over 90-odd seconds is not nearly as “large, dangerous, [and] unstoppable” as two, 3.8m Shuttle RSRMs producing more than 11,500kN thrust over 120-plus seconds. The energies involved in the Atlas V SRB are an order of magnitude smaller than the Shuttle RSRMs, you’re only dealing with one SRB, and the firing time is nearly 25% shorter.

An Atlas V SRB is still a crew abort threat, and it would be best to avoid altogether. But it’s not an enormously unmanageable crew abort threat like the massive Shuttle SRBs.

If SpaceX is planning to do the first FH launch in california, that last i read anyway, are they going to build a throwaway crane to raise it up with empty tanks then throw that away to use shuttle tractors? Seems odd you would design it to operate two different ways. horizontal intergration was one of his big selling points.

He also said they would be upgrading the current pad so they could launch either or falcon 9 or the FH.

From the press briefing he gave at the National pressclub he described the florida operation as “two hangers at 90 degrees” and then they would just “roll out” one or the other to launch. I didn’t get the impression from his talk he was going to be using shuttle tractors… maybe it will be easier. 50 tons .. pretty big payload to push to vertical but I would still think it would be faster than the tractor.

“Hmm, interesting. That is not stopping Boeing from flying the CST-100 on an Atlas V 412, which sports a large, dangerous, unstoppable SRB. My guess is they will add at least one more as the spacecraft inevitably gains weight.”

Relative to the shuttle they are small and unlike Ares-1 the solid isn’t the whole first stage. In fact they drop at 99 seconds into the flight. I also rather doubt the cst-100 gains much weight. Orion forgot the lesson the while Apollo could do a LEO mission, if pressed it was overkill for it. You don’t need a spacecraft capable of supporting itself for 6 montths unmanned and undocked, a crew 21 days and having about 1,500 m/s worth of delta V to do a crew run. All the mass of supplies for long duration crew(and the space for storing them), tanks to hold the extra propellant and water, power system capable of supporting the craft undocked for 6 months make for a very heavy craft.

Orion was counting on technology to make it much lighter than Apollo, but NASA imposed requirements (size ect..) along with inability to build the capsule out of composites and use of a conventional hypergolic propusion system instead of lox/methane made for not much mass savings over Apollo.

Not surprising that they would want a separate launch pad from their current SLC-40 set up, which is specific to a single core rocket.

And I believe that somewhere during this last weekend’s Glenn/Carpenter events, either Charlie Bolden or Bob Cabana said they have three potential suitors for LC-39A, so SpaceX isn’t the only one in the mix. I’ll have to see if I can find that reference, or if my middle-aged brain is playing tricks on me again.

He said they’re looking at building a crew access tower for LC-41, for commercial crew. It would service three different types of crew vehicles. Presumably it would be mobile in the sense that it could be removed for non-crew launches.

I’m certainly no engineer, but from my uninformed perspective I don’t think having one system at Vandenberg precludes a different system at KSC’s LC-39A. Keep in mind that most likely SpaceX would build a custom platform and service tower for the Falcon Heavy, that would match up with whatever they have at Vandenberg.

In the Apollo era, the Launch Umbilical Tower was on the mobile launcher, but there was also a Mobile Service Structure that came up the camp and parked on the other side to provide access. Click here to see an image of both.

If NASA takes LC-39A back to a clean pad, then theoretically anyone could roll anything out there, if they had a bottomless pit of money.

You are talking to the wrong people.
No commercial entity is going to use LC-39. That has been stated by the few commercial entities that exist
Spacex is looking to LC-40 for both F9 and FH.
The LC-41 concept is not mobile. The crew arm is just retracted for non crew launches.

As some one who as worked at both NASA and the FAA i can tell you that they are two completely different agencies. I do not think that the FAA should be involved in regulating space. As for the Office of Commercial Space Transportation they are largely responsible for insuring that a launch does not interfere with any aircraft airspace. They are not equipped to handle the regulatory needs of commercial crew launches when it comes to safety. I do, however, think that NASA could learn a lot from the FAA with regard to the regulation business. Unfortunately the fact of the matter is there is not going to be any over site on this until there is an incident.

Also as a quick addition. There is no such thing as a 100% risk free rocket. All we can do is to reduce risk to the best of our ability and insure that there is an abort system that has the capability to detect as many of the probable failures that it can, and safely remove the crew from harms way. If, as a nation, we demand no failures then there is no point in continuing the space program.

As for the Office of Commercial Space Transportation they are largely responsible for insuring that a launch does not interfere with any aircraft airspace.

Nonsense. They are responsible for much more than that (e.g., ensuring no damage to uninvolved third parties, no EMI interference with other systems, environmental issues, payload compliance with national security requirements, all issues relating to the OST and Liability Convention, etc.), though they do not currently have statutory authority to regulate passenger safety. No one does.

The point is that the Shuttle SRBs on SLS pose a crew abort risk for about 30% longer than the Atlas 412 SRB. That’s significant.

“The hazards are similar.”

The hazards are not quantitatively “similar”.

A Shuttle SRB has a thrust level an order of magnitude higher (10x) than the Atlas V SRB. And there are two Shuttle SRBs compared to the one Atlas V SRB. That makes it much harder for MPCV to get away from and avoid a collision with the Shuttle SRBs in the event of an abort during the first 90-odd seconds of flight.

If the SRBs have to be ripped open during the abort, the radiant heat from the burning propellant on the two, big Shuttle SRBs is also going to extend over a much larger volume than the one, small, Atlas V SRB. This is going to make it much more difficult for the MPCV to navigate a landing without its parachute burning up and dropping the crew to their death in the event of an abort during the first 90-odd seconds of flight.

On top of all that, the two Shuttle SRBs fire for 120-odd seconds, and thus expose the crew to these abort risks for 30% longer than the Atlas V SRB.

Put it this way — if you’re in a car, which is much more difficult to get away from? A kamikaze driver in a Honda carrying a black powder bomb and only enough gas for 90 seconds of driving? Or two kamikaze drivers in two Ferraris, each packed with C4 and enough gas for 120 seconds of driving?

“Thank you are acknowledging my point”

I did not acknowledge your point. The threat posed by the Atlas V SRB to a CST-100 abort is not comparable the threat posed by the Shuttle SRBs to an MPCV abort.

I’m not the only one who thinks so. The Air Force has raised serious concerns about the Shuttle SRBs in a capsule abort, but has raised no such concerns about the Atlas V SRB.

I never questioned the judgement of the Boeing engineers. I questioned your assertion that the threat posed by the Atlas V SRB to a CST-100 abort is comparable the threat posed by the Shuttle SRBs to an MPCV abort. It’s not.

If the SRBs have to be ripped open during the abort, the radiant heat from the burning propellant on the two, big Shuttle SRBs is also going to extend over a much larger volume than the one, small, Atlas V SRB.

It is not ‘radiant heat’ that is the hazard. It is uncontained burning chemicals! The argument could be made for a ruptured propellant tank. The escape system is designed to pull the capsule away, vertically and laterally. The hazards are no different. I can see you have not done FMEA before.

The threat posed by the Atlas V SRB to a CST-100 abort is not comparable the threat posed by the Shuttle SRBs to an MPCV abort.

You are one of the yahoos speaking in extremes about SRBs in manned applications. I was just trying to point out the fallacy of your thinking, and I think I’ve done that.

“It is not ‘radiant heat’ that is the hazard. It is uncontained burning chemicals!”

It is the radiant heat from the burning aluminum in the deflagrating and raining solid propellant elements that is most likely to melt the plastics in a capsule’s parachute and cause a failure. In the event that the range safety officer has to activate the shape charge on an SRB and rupture it — or the SRB detonates/deflagrates on its own — this is the biggest risk to the capsule. The likelihood of actual pieces of solid propellant from a deflagrating SRB making contact with the parachute and directly burning holes in it is less.

“The argument could be made for a ruptured propellant tank.”

No, it couldn’t. Unlike a solid rocket motor, liquid propellant in a tank is not burning or even rapidly expanding when it is ruptured. You have to introduce an external flame or high heat source in the right environment, like the flame from an SRB o-ring burn-through as happened on Challenger, for example. In the absence of an external flame/heat source, a mere ruptured liquid propellant tank will just vent propellant.

“The escape system is designed to pull the capsule away, vertically and laterally.”

Of course.

But that means nothing if the escape system can’t pull you away faster than a high-thrust SRB is chasing you.

And it means nothing if you have two high-thrust SRBs chasing you from different angles, giving you a very narrow or no escape trajectory.

And it means nothing if the thermal environment from a deflagrating SRB is too large to navigate your capsule and its parachute around.

“The hazards are no different.”

They are qualitatively the same but quantitatively they are very, very different. Shuttle SRBs contain an order of magnitude more energy than Atlas V SRBs, they’re firing for 30% longer, and there’s two of them.

“I can see you have not done FMEA before.”

I can see that you know nothing about FMEA.

In FMEA, you analyze both the severity _and_ likelihood of an event.

In this case, the Shuttle SRBs have a greater likelihood of colliding with a capsule than the Atlas V SRB because they burn longer, they’re faster, and there’s two of them.

Also in this case, the much greater energies involved in two, big Shuttle SRBs creates a much larger thermal environment for a capsule to navigate around than one, small, Atlas V SRB, again increasing the likelihood that the plastics in the capsule’s parachute will be compromised and the capsule will plummet to the ground.

“You are one of the yahoos speaking in extremes about SRBs in manned applications.”

It’s not extreme to state that two SRBs that fire for ~30% more time and possess 10x more energy pose a much greater risk to a safe crew abort than one SRB that fires for 30% less time and possesses 10x less energy.

Given these numbers, only an idiot would claim that the Shuttle and Atlas SRBs pose comparable risks to a safe crew abort.

It’s like claiming that two M-80 firecrackers pose the same risk as one little Black Cat firecracker. Or that two .44 Magnums pose the same risk as a BB gun. All are dangerous to a degree, but only an idiot would say that the former examples are as dangerous as the latter examples.

“I was just trying to point out the fallacy of your thinking,”

All you’ve done is put your own utter ignorance on display about FMEA fundamentals, the differences between various SRB designs, and the differences between qualitative and quantitative analysis.

“pathfinder – What the hell kinds of architectures was Griffin thinking about?”

He wanted the ability to land at any point on the moon and did not want to use L1/l2 staging to do so. The drives some requirements delta V and time it takes to return home.

The 6 months unmanned and undocked was due to ability to support a moon base (i.e. leave Orion in a parking orbit and return). This however causes an interesting problem because fuel cells are not a good trade over this amount of time. So instead of fuel cells, Orion would use solar panel and battery plus water tank for crew.

The capsule was also sized to support 6 to LEO and 4 to the moon. But the mass of the capsule is too much for the parachute system to handle loaded with 6 people and thus the crew is stuck at 4.